The droid tank seems to be the best choice for leveling up. By pulling aggro it allows you to get off an uninterrupted full auto. With Elara you lose DPS due to pushback. To heal the droid just mount and unmount which returns 100% of health. The only downside is that the droid tends to pull extra mobs at times, especially when you are in an area with a lot of densely packed mobs. I don't know how well Assault Specialist levels, but Gunnery is very effective.
You will want to use AoE at every opportunity. Try to find ways of using pulse cannon, sticky grenade, plasma grenade, and hail of bolts whenever possible. Always use mortar volley when it is off CD. Other than that, use the standard full auto, gravround, HIB, Demo round rotation.